So you're going to a costume party in a bad neighborhood. You want to be safe, but you don't want to break out of your historical character. Take this quick tutorial on how to make a jar, invented in the 1700s, that stores up enough static electricity to disable, or even kill someone.

If we are going to think about the Leyden Jar in historical context, the first thing to know is that it fits in nicely with scientific tradition, by not being named by the first person to invent it. The first person to trap lightning in a jar was a Prussian man by the name of Ewald von Kleist, in 1744. In 1746, in the Dutch city of Leyden, Pieter van Musschenbroek also invented the jar, and the name he gave it, for the town he invented it in, has stuck ever since.

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A Leyden Jar is remarkably easy to make and charge. Grab a glass jar with a metal cap. Line both the inside and the outside of the jar with foil, leaving a couple inches of glass clear at the top of the jar, so that the inner and outer foil can never touch. Next get a nail and drive it through the jar lid until it touches the foil inside the jar. If it can't quite touch the inner foil, add a length of metal chain or wire to it. You've made the jar, now you just have to charge it. In the old days, they rubbed a glass rod with silk or fur, and then rubbed the top of the nail with the tube. Today that will still work, but so will a length of PVC pipe brushed with paper.

The inner and the outer foil are close to each other, so they both acquire a charge. The problem is, the glass insulates them - this will also work with a plastic jar - and so they can't even out the difference in charge between the two. When someone touches the foil on the outside and touches the nail sticking out of the inside, the electrons rush through them and they get a shock. To taserize the jar, all you need to do is add a length of wire to the outside of the jar, and bring it up close to, but not touching, the head of the nail. Jam both of the parts against an attacker, and you went Enlightenment on their ass.

The jar, although small, can pack a punch. Now people use powder or liquid inside the jar to hold more charge, and use machines to charge the jar up. Even in the old days, though, it was used for destruction. Scientific demonstrations were held during which the jars were used to kill small animals and birds in front of an audience. More misanthropic scientists engineered jars to increase the overall shock that they gave off, and used them on large numbers of human subjects. They were able to get away with this because all the subjects felt the shock at once.

Jean-Antoine Nollet became famous for this for once getting a bunch of monks to hold a metal wire before applying the jar to the wire, causing all the monks to yell in shock, and then doing the whole trick over again by getting 180 Royal Guards to hold hands in front of Louis XV and sending a shock through the lot of them. Presumably, after that, people got wise to his tricks.

The Leyden Jar became an early way to create a set amount electricity in one place, and then carry around, having it always at the ready. In modern terms, the Leyden Jar is a capacitor, and versions of it are what make camera flashes go off on command whenever we want them to. Scientists used them to conduct electrical experiments. Ben Franklin, scientists extraordinaire, connected many jars together and called them a 'battery,' referring to the military idea of multiple weapons meant to be used simultaneously. The Leyden Jar was the first step down a long road of ever-evolving uses for electricity.

It will, however, knock a person flat if you layer enough foil and build up enough charge — so use it carefully, party-goers.